A number of different explosive devices are used in oil and gas well operations. Perforating guns are used to fire shape charges. The firing of the shape charges creates additional surface area in the well, to improve production rates. The shape charges in perforating guns are highly explosive, and extreme caution must be used by personnel handling the guns or charges. Other explosive devices which are used in oil and gas well downhole applications include squibs, setting tools, ignitors, core guns, and chemical cutters.
Many of these explosive devices are electric-fired. That is, a current of electricity is used to initiate the explosion. For the safety of personnel, it is imperative that an electrical current does not reach the explosive device while the device is on the surface.
Electrical currents can be accidentally induced into the wiring circuit of an explosive device in any number of ways. One way is via human error. Other ways include short circuits, stray voltage, welding equipment, static electricity, and RF energies such as helicopter radar, microwave, CB radio, ship-to-shore, and cellular telephones. To prevent an accidental electrical current, it is typical that the entire rig and the surrounding area has to alter its activities. This causes delay and expense, and can be difficult to manage.
Therefore, what is needed is a device and method for preventing electrical currents from accidentally triggering an explosive device while it is on the surface, while still allowing the explosive device to be activated downhole.